• 1981 B7 turbo

Alpina archaelogy

Updated: Sep 24, 2020

In telling the stories here the topics are usually presented linearly. But the reality is usually very different; projects often overlap, one waiting for parts and then something critical needs to be fixed ASAP, or life just intervenes. It’s not unusual to be juggling a couple of different repairs at the same time. This is typical of any project car. But the B7 has an added challenge: trying to figure out the differences between a stock e12 and the B7 and then finding the B7-unique parts creates plenty of delays. Call it Alpina archaelogy. And it presents itself in weird ways.

After buttoning-up the suspension, I dropped the car down on the ground and took it for a test drive to let the suspension settle and get a feel for how it handles with the new bits installed. As I’m pulling in the garage at the end of the drive I hear a noise that’s somewhere between a metallic rubbing sound and brake squeaking. I park the car and am somewhere between (1) pissed there's another issue and (2) puzzling over what the sound could be.

Calmed, I go out a few days later to listen again and diagnose. About a half mile from my house and the car sputters and recovers. A mile later, again. And then again. Two miles further it dies, not to restart. I call AAA; they tell me it will be 45 minutes for a tow truck to get there, so I sit there (closer to pissed than puzzled) watching everybody staring at the vintage car with it’s hood up. 15 minutes into the 45 minute wait I try to start it again and it fires up, perfectly happy. I drive home, all fine, cancel the tow truck and trouble-shoot the new problem. I figured it was likely fuel related. I text and email two mechanic friends and there’s a consensus: classic symptoms of a fuel pump relay faliure.

A fuel pump relay should be an easy thing to trouble-shoot, right? Wrong, cuz you gotta find the fuel pump relay first. The stock e12 comes with Bosch L injection, which uses low pressure fuel pumps and the B7 has Pierburg injection that is similar to Bosch K and uses high pressure. It has different fuel pumps, in different places, which means different wiring (yes, plural, as in two fuel pumps; one under the car near the tank—like a 2002tii—and the second in the engine compartment where the battery resides in a stock e12).

Fuel pump in the battery tray

Fuel pump and filter under the car near the gas tank

Not thinking about the unique fuel pump wiring, I go searching for the e12 fuel pump relay. I look at the diagram on the fuse block cover but it’s in German, a language I’m not too proficient at. So, I turn on the key, listen to the pump (only the rear one is making noise) and pull relays to figure out which one stops the sound of the fuel pump humming. None. A big zero. I go in the house and do internet searches for the relay at my favorite vendors. Zero, not listed. I look on the boards, try to find wiring diagrams, picture of the relays in situ. Nothing helpful. Eventually, I figure out that the stock fuel pump relay is part of the Bosch L Jet wiring and is far away from the fuse block. That doesn’t help me find mine as none of the Bosch L injection or wiring remains.

I know three people with an e12 B7. I message two of them (one in England, one in SoCal). They both tell me where the relay is in their car, but the relay, while in a similar spot, is not in exactly the same place. (Alpina added two relays on the outside of the fuse block; in the pictures they sent me one was in the forward position, the other in the rearward. Mine was the rear as well.). While the relays were not in the same spot, they looked the same as mine.

Two relays outside fuse block, one closer to top is fuel pump relay

Fuel pump peaking out from under the washer bottle, fuel pump relay outside of fuse block, on right

Now that I’ve located the relay, out to the garage and, with the key on, I pull that relay. But the rear pump is still humming. With the relay out, I try to start the car but it won’t fire. I put the relay back in and try to start it: vroom, starts right up! Seems the front pump is wired to the relay but not the rear. Does the rear have no relay? No fuse? I have no idea.

Anyway, having found the right relay, I take a picture of it and type the part number in google. A search shows it’s the same as used in BMWs with Bosch K, like an e21 320i or 323i. The BMW relay is $175.00 from my preferred vendor. Same elsewhere. And no matter how hard I search, I can’t find a relay with the same number in the aftermarket. But there is an aftermarket relay for $23.00 by K.A.E., a manufacturer I’ve never heard of.

K.A.E. on left, BMW on right

So, I order the K.A.E. relay. Two actually, an extra to keep in the glove box. Having never heard of K.A.E., I figured better safe than sorry having a backup and the two relays together were still less than half of the BMW relay—which is probably made by K.A.E.


This type of archaeological dig in typical with Alpinas. In one of my blog posts about the 1982 e21 Alpina C1 2.3 that I’m (very slowly) restoring, I write about “the mystery and allure of Alpinas” ( That post discussed verifying whether a non-documented car was a real-deal Alpina. But it applies here too: part of mystery and allure “was that you kinda never really knew what you had.” Understanding the wiring for the fuel pump relay, locating the fuel pump relay, figuring out which pumps were powered by that relay—those are all part of a mystery to be solved. A puzzle to be put together.

And these little mysteries and puzzles side-track progress on the bigger projects. Trouble-shooting the squeaking noise and dialing the suspension in got side tracked by a little drivability issue because of the relay. Unable or unwilling to drive the car until the fuel issue was resolved (or at least until I could test the relay theory), progress on the suspension and trouble-shooting the brakes took a back-seat. With the new fuel pump relay in, I could test drive again and make some progress on the other issues.

When I got back to the brakes, it was another archeological dig. In trouble-shooting the noise, I decided in to change the rotors and pads. I wanted to do this for two reasons: first, I suspected the noise was the pads and changing the rotors and pads was a logical place to start and, secondly, because the front rotors are Alpina-unique (being both vented and slotted, with a big ALPINA engraved on them). The 4-piston calipers were also Alpina-unique, having a spacer in them to fit over the vented rotor (similar to Alpina front brake kits for a 2002tii). Since the e12 did not have vented rotors, obviously neither were stock for an e12. Ideally, I could find a BMW part that fit and preserve the Alpina-unique parts.

The slotted Alpina rotor

I first check with a fellow B7 owner who told me the Alpina rotors are NLA and it costs about $750 to have custom rotors made. I wondered whether the Alpina rotor was simply a BMW rotor that had been slotted and then marked “ALPINA.” To test that theory, I had to find out the size of the Alpina rotors. My first stop was to email Alpina. They took a while to get back to me, but eventually told me the front rotors were 300mmx30mm and the rears were 272x19, but neither were available from Alpina. They offered no help on fronts and said to check with BMW for the rears, implying 272x19 was a stock size.

While waiting for Alpina to email back, the B7 owner who had told me about the front rotors happened to post about his build sheet. I asked him to share it and it listed front rotors as 280x28. I then remembered that the previous owner had provided me with a build sheet for this car; I checked that: 280x28. Funny that Alpina told me a different size and I was a bit unsure.

BMW e28 M5 rotors (among others) are 300x30 but I wasn’t going to pay the steep price for them when it seemed the rotors were 280mm diameter. But, I couldn’t find any 280mm BMW rotors that were 28mm wide. There were, however, 280x25 vented rotors used on the e23 7-series. Would those fit? I was hopeful—the cars are of similar vintage and the BMW part was thinner, mean it should fit within the pads. There was only one way to find out—and they were cheap, just not slotted or cross-drilled. I ordered a couple.

Stock BMW 7-series rotor (280x25) on left, Alpina (280x28) on right

With the car back up on jack-stands, I test the theory and they fit. Out for a test drive and the brakes work the same as before, stopping the car just like they should. Again, the 7-series rotors were vented (obviously) but not slotted. But I guess I’ll use these and save the original Alpina NLA rotors. I may replace the stock 7-series discs with a cross-drilled version (Alpina used both slotted and cross-drilled rotors). But, as these were a non-refundable special order, I didn’t want to spend that kind of money before I knew they’d fit.

It seems the rear brakes are stock BMW, but not standard e-12 brakes. The stock e12 rear rotors are not vented and are 272x10. Not only did Alpina tell me to check with BMW for the rears, the rear rotors on the car are vented but have no unique Alpina marking. A little Internet sleuthing reveals that the rear rotors for the e9 and e24 6-series are the same size (272x19), so I assume those will fit fine.

Not every project gets sidetracked by an archaeological dig, but it ain’t rare either. But the dig is fun, trying to figure out what a bunch of smart Germans did some 40 years ago.

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